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class="sidebar-link">16_变量进阶(理解)</a></li><li><a href="/vdoing-demo-repository/pages/f99095/" aria-current="page" class="active sidebar-link">17_函数进阶</a><ul class="sidebar-sub-headers"><li class="sidebar-sub-header level2"><a href="/vdoing-demo-repository/pages/f99095/#目标" class="sidebar-link">目标</a></li><li class="sidebar-sub-header level2"><a href="/vdoing-demo-repository/pages/f99095/#_01-函数参数和返回值的作用" class="sidebar-link">01. 函数参数和返回值的作用</a><ul class="sidebar-sub-headers"><li class="sidebar-sub-header level3"><a href="/vdoing-demo-repository/pages/f99095/#_1-1-无参数-无返回值" class="sidebar-link">1.1 无参数，无返回值</a></li><li class="sidebar-sub-header level3"><a href="/vdoing-demo-repository/pages/f99095/#_1-2-无参数-有返回值" class="sidebar-link">1.2 无参数，有返回值</a></li><li class="sidebar-sub-header level3"><a href="/vdoing-demo-repository/pages/f99095/#_1-3-有参数-无返回值" class="sidebar-link">1.3 有参数，无返回值</a></li><li class="sidebar-sub-header level3"><a href="/vdoing-demo-repository/pages/f99095/#_1-4-有参数-有返回值" class="sidebar-link">1.4 有参数，有返回值</a></li></ul></li><li class="sidebar-sub-header level2"><a href="/vdoing-demo-repository/pages/f99095/#_02-函数的返回值-进阶" class="sidebar-link">02. 函数的返回值 进阶</a><ul class="sidebar-sub-headers"><li class="sidebar-sub-header level3"><a href="/vdoing-demo-repository/pages/f99095/#示例-温度和湿度测量" class="sidebar-link">示例 —— 温度和湿度测量</a></li><li class="sidebar-sub-header level3"><a href="/vdoing-demo-repository/pages/f99095/#面试题-交换两个数字" class="sidebar-link">面试题 —— 交换两个数字</a></li></ul></li><li class="sidebar-sub-header level2"><a href="/vdoing-demo-repository/pages/f99095/#_03-函数的参数-进阶" class="sidebar-link">03. 函数的参数 进阶</a><ul class="sidebar-sub-headers"><li class="sidebar-sub-header level3"><a href="/vdoing-demo-repository/pages/f99095/#_3-1-不可变和可变的参数" class="sidebar-link">3.1. 不可变和可变的参数</a></li><li class="sidebar-sub-header level3"><a href="/vdoing-demo-repository/pages/f99095/#_3-2-缺省参数" class="sidebar-link">3.2 缺省参数</a></li><li class="sidebar-sub-header level3"><a href="/vdoing-demo-repository/pages/f99095/#_3-3-多值参数-知道" class="sidebar-link">3.3 多值参数（知道）</a></li></ul></li><li class="sidebar-sub-header level2"><a href="/vdoing-demo-repository/pages/f99095/#_04-函数的递归" class="sidebar-link">04. 函数的递归</a><ul class="sidebar-sub-headers"><li class="sidebar-sub-header level3"><a href="/vdoing-demo-repository/pages/f99095/#_4-1-递归函数的特点" class="sidebar-link">4.1 递归函数的特点</a></li><li class="sidebar-sub-header level3"><a href="/vdoing-demo-repository/pages/f99095/#_4-2-递归案例-计算数字累加" class="sidebar-link">4.2 递归案例 —— 计算数字累加</a></li></ul></li></ul></li></ul> </aside> <div><main class="page"><div class="theme-vdoing-wrapper "><div class="articleInfo-wrap" data-v-06225672><div class="articleInfo" data-v-06225672><ul class="breadcrumbs" data-v-06225672><li data-v-06225672><a href="/vdoing-demo-repository/" title="首页" class="iconfont icon-home router-link-active" data-v-06225672></a></li> <li data-v-06225672><a href="/vdoing-demo-repository/python/#Python" data-v-06225672>Python</a></li></ul> <div class="info" data-v-06225672><!----> <div title="创建时间" class="date iconfont icon-riqi" data-v-06225672><a href="javascript:;" data-v-06225672>2023-04-02</a></div> <!----></div></div></div> <!----> <div class="content-wrapper"><div class="right-menu-wrapper"><div class="right-menu-margin"><div class="right-menu-title">目录</div> <div class="right-menu-content"></div></div></div> <h1><img src="">17_函数进阶<!----></h1> <!----> <div class="theme-vdoing-content content__default"><h1 id="函数进阶"><a href="#函数进阶" class="header-anchor">#</a> 函数进阶</h1> <h2 id="目标"><a href="#目标" class="header-anchor">#</a> 目标</h2> <ul><li>函数参数和返回值的作用</li> <li>函数的返回值 进阶</li> <li>函数的参数 进阶</li> <li>递归函数</li></ul> <h2 id="_01-函数参数和返回值的作用"><a href="#_01-函数参数和返回值的作用" class="header-anchor">#</a> 01. 函数参数和返回值的作用</h2> <p>函数根据 <strong>有没有参数</strong> 以及 <strong>有没有返回值</strong>，可以 <strong>相互组合</strong>，一共有 <strong>4 种</strong> 组合形式</p> <ol><li>无参数，无返回值</li> <li>无参数，有返回值</li> <li>有参数，无返回值</li> <li>有参数，有返回值</li></ol> <p><img src="media/14993074876434/001_%E5%87%BD%E6%95%B0%E5%8F%82%E6%95%B0%E5%92%8C%E8%BF%94%E5%9B%9E%E5%80%BC.png" alt="001_函数参数和返回值"></p> <blockquote><p>定义函数时，<strong>是否接收参数，或者是否返回结果</strong>，是根据 <strong>实际的功能需求</strong> 来决定的！</p></blockquote> <ol><li>如果函数 <strong>内部处理的数据不确定</strong>，就可以将外界的数据以参数传递到函数内部</li> <li>如果希望一个函数 <strong>执行完成后，向外界汇报执行结果</strong>，就可以增加函数的返回值</li></ol> <h3 id="_1-1-无参数-无返回值"><a href="#_1-1-无参数-无返回值" class="header-anchor">#</a> 1.1 无参数，无返回值</h3> <p>此类函数，不接收参数，也没有返回值，应用场景如下：</p> <ol><li><strong>只是单纯地做一件事情</strong>，例如 <strong>显示菜单</strong></li> <li>在函数内部 <strong>针对全局变量进行操作</strong>，例如：<strong>新建名片</strong>，最终结果 <strong>记录在全局变量</strong> 中</li></ol> <blockquote><p>注意：</p></blockquote> <ul><li>如果全局变量的数据类型是一个 <strong>可变类型</strong>，在函数内部可以使用 <strong>方法</strong> 修改全局变量的内容 —— <strong>变量的引用不会改变</strong></li> <li>在函数内部，<strong>使用赋值语句</strong> 才会 <strong>修改变量的引用</strong></li></ul> <h3 id="_1-2-无参数-有返回值"><a href="#_1-2-无参数-有返回值" class="header-anchor">#</a> 1.2 无参数，有返回值</h3> <p>此类函数，不接收参数，但是有返回值，应用场景如下：</p> <ul><li>采集数据，例如 <strong>温度计</strong>，返回结果就是当前的温度，而不需要传递任何的参数</li></ul> <h3 id="_1-3-有参数-无返回值"><a href="#_1-3-有参数-无返回值" class="header-anchor">#</a> 1.3 有参数，无返回值</h3> <p>此类函数，接收参数，没有返回值，应用场景如下：</p> <ul><li>函数内部的代码保持不变，针对 <strong>不同的参数 处理 不同的数据</strong></li> <li>例如 <strong>名片管理系统</strong> 针对 <strong>找到的名片</strong> 做 <strong>修改</strong>、<strong>删除</strong> 操作</li></ul> <h3 id="_1-4-有参数-有返回值"><a href="#_1-4-有参数-有返回值" class="header-anchor">#</a> 1.4 有参数，有返回值</h3> <p>此类函数，接收参数，同时有返回值，应用场景如下：</p> <ul><li>函数内部的代码保持不变，针对 <strong>不同的参数 处理 不同的数据</strong>，并且 <strong>返回期望的处理结果</strong></li> <li>例如 <strong>名片管理系统</strong> 使用 <strong>字典默认值</strong> 和 <strong>提示信息</strong> 提示用户输入内容
<ul><li>如果输入，返回输入内容</li> <li>如果没有输入，返回字典默认值</li></ul></li></ul> <h2 id="_02-函数的返回值-进阶"><a href="#_02-函数的返回值-进阶" class="header-anchor">#</a> 02. 函数的返回值 进阶</h2> <ul><li>在程序开发中，有时候，会希望 <strong>一个函数执行结束后，告诉调用者一个结果</strong>，以便调用者针对具体的结果做后续的处理</li> <li><strong>返回值</strong> 是函数 <strong>完成工作</strong>后，<strong>最后</strong> 给调用者的 <strong>一个结果</strong></li> <li>在函数中使用 <code>return</code> 关键字可以返回结果</li> <li>调用函数一方，可以 <strong>使用变量</strong> 来 <strong>接收</strong> 函数的返回结果</li></ul> <blockquote><p>问题：一个函数执行后能否返回多个结果？</p></blockquote> <h3 id="示例-温度和湿度测量"><a href="#示例-温度和湿度测量" class="header-anchor">#</a> 示例 —— 温度和湿度测量</h3> <ul><li>假设要开发一个函数能够同时返回当前的温度和湿度</li> <li><strong>先完成返回温度</strong>的功能如下：</li></ul> <div class="language-python line-numbers-mode"><pre class="language-python"><code><span class="token keyword">def</span> <span class="token function">measure</span><span class="token punctuation">(</span><span class="token punctuation">)</span><span class="token punctuation">:</span>
    <span class="token triple-quoted-string string">&quot;&quot;&quot;返回当前的温度&quot;&quot;&quot;</span>
    
    <span class="token keyword">print</span><span class="token punctuation">(</span><span class="token string">&quot;开始测量...&quot;</span><span class="token punctuation">)</span>
    temp <span class="token operator">=</span> <span class="token number">39</span>
    <span class="token keyword">print</span><span class="token punctuation">(</span><span class="token string">&quot;测量结束...&quot;</span><span class="token punctuation">)</span>
    
    <span class="token keyword">return</span> temp

result <span class="token operator">=</span> measure<span class="token punctuation">(</span><span class="token punctuation">)</span>
<span class="token keyword">print</span><span class="token punctuation">(</span>result<span class="token punctuation">)</span>
</code></pre> <div class="line-numbers-wrapper"><span class="line-number">1</span><br><span class="line-number">2</span><br><span class="line-number">3</span><br><span class="line-number">4</span><br><span class="line-number">5</span><br><span class="line-number">6</span><br><span class="line-number">7</span><br><span class="line-number">8</span><br><span class="line-number">9</span><br><span class="line-number">10</span><br><span class="line-number">11</span><br></div></div><ul><li>在利用 <strong>元组</strong> 在返回温度的同时，也能够返回 <strong>湿度</strong></li> <li>改造如下：</li></ul> <div class="language-python line-numbers-mode"><pre class="language-python"><code><span class="token keyword">def</span> <span class="token function">measure</span><span class="token punctuation">(</span><span class="token punctuation">)</span><span class="token punctuation">:</span>
    <span class="token triple-quoted-string string">&quot;&quot;&quot;返回当前的温度&quot;&quot;&quot;</span>

    <span class="token keyword">print</span><span class="token punctuation">(</span><span class="token string">&quot;开始测量...&quot;</span><span class="token punctuation">)</span>
    temp <span class="token operator">=</span> <span class="token number">39</span>
    wetness <span class="token operator">=</span> <span class="token number">10</span>
    <span class="token keyword">print</span><span class="token punctuation">(</span><span class="token string">&quot;测量结束...&quot;</span><span class="token punctuation">)</span>

    <span class="token keyword">return</span> <span class="token punctuation">(</span>temp<span class="token punctuation">,</span> wetness<span class="token punctuation">)</span>
</code></pre> <div class="line-numbers-wrapper"><span class="line-number">1</span><br><span class="line-number">2</span><br><span class="line-number">3</span><br><span class="line-number">4</span><br><span class="line-number">5</span><br><span class="line-number">6</span><br><span class="line-number">7</span><br><span class="line-number">8</span><br><span class="line-number">9</span><br></div></div><blockquote><p>提示：如果一个函数返回的是元组，括号可以省略</p></blockquote> <p><strong>技巧</strong></p> <ul><li>在 <code>Python</code> 中，可以 <strong>将一个元组</strong> 使用 <strong>赋值语句</strong> 同时赋值给 <strong>多个变量</strong></li> <li>注意：变量的数量需要和元组中的元素数量保持一致</li></ul> <div class="language-python line-numbers-mode"><pre class="language-python"><code>result <span class="token operator">=</span> temp<span class="token punctuation">,</span> wetness <span class="token operator">=</span> measure<span class="token punctuation">(</span><span class="token punctuation">)</span>
</code></pre> <div class="line-numbers-wrapper"><span class="line-number">1</span><br></div></div><h3 id="面试题-交换两个数字"><a href="#面试题-交换两个数字" class="header-anchor">#</a> 面试题 —— 交换两个数字</h3> <p><strong>题目要求</strong></p> <ol><li>有两个整数变量 <code>a = 6</code>, <code>b = 100</code></li> <li>不使用其他变量，<strong>交换两个变量的值</strong></li></ol> <h4 id="解法-1-使用其他变量"><a href="#解法-1-使用其他变量" class="header-anchor">#</a> 解法 1 —— 使用其他变量</h4> <div class="language-python line-numbers-mode"><pre class="language-python"><code><span class="token comment"># 解法 1 - 使用临时变量</span>
c <span class="token operator">=</span> b
b <span class="token operator">=</span> a
a <span class="token operator">=</span> c
</code></pre> <div class="line-numbers-wrapper"><span class="line-number">1</span><br><span class="line-number">2</span><br><span class="line-number">3</span><br><span class="line-number">4</span><br></div></div><h4 id="解法-2-不使用临时变量"><a href="#解法-2-不使用临时变量" class="header-anchor">#</a> 解法 2 —— 不使用临时变量</h4> <div class="language-python line-numbers-mode"><pre class="language-python"><code><span class="token comment"># 解法 2 - 不使用临时变量</span>
a <span class="token operator">=</span> a <span class="token operator">+</span> b
b <span class="token operator">=</span> a <span class="token operator">-</span> b
a <span class="token operator">=</span> a <span class="token operator">-</span> b
</code></pre> <div class="line-numbers-wrapper"><span class="line-number">1</span><br><span class="line-number">2</span><br><span class="line-number">3</span><br><span class="line-number">4</span><br></div></div><h4 id="解法-3-python-专有-利用元组"><a href="#解法-3-python-专有-利用元组" class="header-anchor">#</a> 解法 3 —— Python 专有，利用元组</h4> <div class="language-python line-numbers-mode"><pre class="language-python"><code>a<span class="token punctuation">,</span> b <span class="token operator">=</span> b<span class="token punctuation">,</span> a
</code></pre> <div class="line-numbers-wrapper"><span class="line-number">1</span><br></div></div><h2 id="_03-函数的参数-进阶"><a href="#_03-函数的参数-进阶" class="header-anchor">#</a> 03. 函数的参数 进阶</h2> <h3 id="_3-1-不可变和可变的参数"><a href="#_3-1-不可变和可变的参数" class="header-anchor">#</a> 3.1. 不可变和可变的参数</h3> <blockquote><p>问题 1：在函数内部，针对参数使用 <strong>赋值语句</strong>，会不会影响调用函数时传递的 <strong>实参变量</strong>？ —— 不会！</p></blockquote> <ul><li>无论传递的参数是 <strong>可变</strong> 还是 <strong>不可变</strong> <ul><li>只要 <strong>针对参数</strong> 使用 <strong>赋值语句</strong>，会在 <strong>函数内部</strong> 修改 <strong>局部变量的引用</strong>，<strong>不会影响到 外部变量的引用</strong></li></ul></li></ul> <div class="language-python line-numbers-mode"><pre class="language-python"><code><span class="token keyword">def</span> <span class="token function">demo</span><span class="token punctuation">(</span>num<span class="token punctuation">,</span> num_list<span class="token punctuation">)</span><span class="token punctuation">:</span>

    <span class="token keyword">print</span><span class="token punctuation">(</span><span class="token string">&quot;函数内部&quot;</span><span class="token punctuation">)</span>

    <span class="token comment"># 赋值语句</span>
    num <span class="token operator">=</span> <span class="token number">200</span>
    num_list <span class="token operator">=</span> <span class="token punctuation">[</span><span class="token number">1</span><span class="token punctuation">,</span> <span class="token number">2</span><span class="token punctuation">,</span> <span class="token number">3</span><span class="token punctuation">]</span>

    <span class="token keyword">print</span><span class="token punctuation">(</span>num<span class="token punctuation">)</span>
    <span class="token keyword">print</span><span class="token punctuation">(</span>num_list<span class="token punctuation">)</span>

    <span class="token keyword">print</span><span class="token punctuation">(</span><span class="token string">&quot;函数代码完成&quot;</span><span class="token punctuation">)</span>


gl_num <span class="token operator">=</span> <span class="token number">99</span>
gl_list <span class="token operator">=</span> <span class="token punctuation">[</span><span class="token number">4</span><span class="token punctuation">,</span> <span class="token number">5</span><span class="token punctuation">,</span> <span class="token number">6</span><span class="token punctuation">]</span>
demo<span class="token punctuation">(</span>gl_num<span class="token punctuation">,</span> gl_list<span class="token punctuation">)</span>
<span class="token keyword">print</span><span class="token punctuation">(</span>gl_num<span class="token punctuation">)</span>
<span class="token keyword">print</span><span class="token punctuation">(</span>gl_list<span class="token punctuation">)</span>
    
</code></pre> <div class="line-numbers-wrapper"><span class="line-number">1</span><br><span class="line-number">2</span><br><span class="line-number">3</span><br><span class="line-number">4</span><br><span class="line-number">5</span><br><span class="line-number">6</span><br><span class="line-number">7</span><br><span class="line-number">8</span><br><span class="line-number">9</span><br><span class="line-number">10</span><br><span class="line-number">11</span><br><span class="line-number">12</span><br><span class="line-number">13</span><br><span class="line-number">14</span><br><span class="line-number">15</span><br><span class="line-number">16</span><br><span class="line-number">17</span><br><span class="line-number">18</span><br><span class="line-number">19</span><br><span class="line-number">20</span><br></div></div><blockquote><p>问题 2：如果传递的参数是 <strong>可变类型</strong>，在函数内部，使用 <strong>方法</strong> 修改了数据的内容，<strong>同样会影响到外部的数据</strong></p></blockquote> <div class="language-python line-numbers-mode"><pre class="language-python"><code><span class="token keyword">def</span> <span class="token function">mutable</span><span class="token punctuation">(</span>num_list<span class="token punctuation">)</span><span class="token punctuation">:</span>

    <span class="token comment"># num_list = [1, 2, 3]</span>
    num_list<span class="token punctuation">.</span>extend<span class="token punctuation">(</span><span class="token punctuation">[</span><span class="token number">1</span><span class="token punctuation">,</span> <span class="token number">2</span><span class="token punctuation">,</span> <span class="token number">3</span><span class="token punctuation">]</span><span class="token punctuation">)</span>
    
    <span class="token keyword">print</span><span class="token punctuation">(</span>num_list<span class="token punctuation">)</span>

gl_list <span class="token operator">=</span> <span class="token punctuation">[</span><span class="token number">6</span><span class="token punctuation">,</span> <span class="token number">7</span><span class="token punctuation">,</span> <span class="token number">8</span><span class="token punctuation">]</span>
mutable<span class="token punctuation">(</span>gl_list<span class="token punctuation">)</span>
<span class="token keyword">print</span><span class="token punctuation">(</span>gl_list<span class="token punctuation">)</span>
</code></pre> <div class="line-numbers-wrapper"><span class="line-number">1</span><br><span class="line-number">2</span><br><span class="line-number">3</span><br><span class="line-number">4</span><br><span class="line-number">5</span><br><span class="line-number">6</span><br><span class="line-number">7</span><br><span class="line-number">8</span><br><span class="line-number">9</span><br><span class="line-number">10</span><br></div></div><h4 id="面试题"><a href="#面试题" class="header-anchor">#</a> 面试题 —— <code>+=</code></h4> <ul><li>在 <code>python</code> 中，列表变量调用 <code>+=</code> 本质上是在执行列表变量的 <code>extend</code> 方法，不会修改变量的引用</li></ul> <div class="language-python line-numbers-mode"><pre class="language-python"><code><span class="token keyword">def</span> <span class="token function">demo</span><span class="token punctuation">(</span>num<span class="token punctuation">,</span> num_list<span class="token punctuation">)</span><span class="token punctuation">:</span>

    <span class="token keyword">print</span><span class="token punctuation">(</span><span class="token string">&quot;函数内部代码&quot;</span><span class="token punctuation">)</span>

    <span class="token comment"># num = num + num</span>
    num <span class="token operator">+=</span> num
    <span class="token comment"># num_list.extend(num_list) 由于是调用方法，所以不会修改变量的引用</span>
    <span class="token comment"># 函数执行结束后，外部数据同样会发生变化</span>
    num_list <span class="token operator">+=</span> num_list

    <span class="token keyword">print</span><span class="token punctuation">(</span>num<span class="token punctuation">)</span>
    <span class="token keyword">print</span><span class="token punctuation">(</span>num_list<span class="token punctuation">)</span>
    <span class="token keyword">print</span><span class="token punctuation">(</span><span class="token string">&quot;函数代码完成&quot;</span><span class="token punctuation">)</span>


gl_num <span class="token operator">=</span> <span class="token number">9</span>
gl_list <span class="token operator">=</span> <span class="token punctuation">[</span><span class="token number">1</span><span class="token punctuation">,</span> <span class="token number">2</span><span class="token punctuation">,</span> <span class="token number">3</span><span class="token punctuation">]</span>
demo<span class="token punctuation">(</span>gl_num<span class="token punctuation">,</span> gl_list<span class="token punctuation">)</span>
<span class="token keyword">print</span><span class="token punctuation">(</span>gl_num<span class="token punctuation">)</span>
<span class="token keyword">print</span><span class="token punctuation">(</span>gl_list<span class="token punctuation">)</span>

</code></pre> <div class="line-numbers-wrapper"><span class="line-number">1</span><br><span class="line-number">2</span><br><span class="line-number">3</span><br><span class="line-number">4</span><br><span class="line-number">5</span><br><span class="line-number">6</span><br><span class="line-number">7</span><br><span class="line-number">8</span><br><span class="line-number">9</span><br><span class="line-number">10</span><br><span class="line-number">11</span><br><span class="line-number">12</span><br><span class="line-number">13</span><br><span class="line-number">14</span><br><span class="line-number">15</span><br><span class="line-number">16</span><br><span class="line-number">17</span><br><span class="line-number">18</span><br><span class="line-number">19</span><br><span class="line-number">20</span><br><span class="line-number">21</span><br></div></div><h3 id="_3-2-缺省参数"><a href="#_3-2-缺省参数" class="header-anchor">#</a> 3.2 缺省参数</h3> <ul><li>定义函数时，可以给 <strong>某个参数</strong> 指定一个<strong>默认值</strong>，具有默认值的参数就叫做 <strong>缺省参数</strong></li> <li>调用函数时，如果没有传入 <strong>缺省参数</strong> 的值，则在函数内部使用定义函数时指定的 <strong>参数默认值</strong></li> <li>函数的缺省参数，<strong>将常见的值设置为参数的缺省值</strong>，从而 <strong>简化函数的调用</strong></li> <li>例如：对列表排序的方法</li></ul> <div class="language-python line-numbers-mode"><pre class="language-python"><code>gl_num_list <span class="token operator">=</span> <span class="token punctuation">[</span><span class="token number">6</span><span class="token punctuation">,</span> <span class="token number">3</span><span class="token punctuation">,</span> <span class="token number">9</span><span class="token punctuation">]</span>

<span class="token comment"># 默认就是升序排序，因为这种应用需求更多</span>
gl_num_list<span class="token punctuation">.</span>sort<span class="token punctuation">(</span><span class="token punctuation">)</span>
<span class="token keyword">print</span><span class="token punctuation">(</span>gl_num_list<span class="token punctuation">)</span>

<span class="token comment"># 只有当需要降序排序时，才需要传递 `reverse` 参数</span>
gl_num_list<span class="token punctuation">.</span>sort<span class="token punctuation">(</span>reverse<span class="token operator">=</span><span class="token boolean">True</span><span class="token punctuation">)</span>
<span class="token keyword">print</span><span class="token punctuation">(</span>gl_num_list<span class="token punctuation">)</span>
</code></pre> <div class="line-numbers-wrapper"><span class="line-number">1</span><br><span class="line-number">2</span><br><span class="line-number">3</span><br><span class="line-number">4</span><br><span class="line-number">5</span><br><span class="line-number">6</span><br><span class="line-number">7</span><br><span class="line-number">8</span><br><span class="line-number">9</span><br></div></div><h4 id="指定函数的缺省参数"><a href="#指定函数的缺省参数" class="header-anchor">#</a> 指定函数的缺省参数</h4> <ul><li>在参数后使用赋值语句，可以指定参数的缺省值</li></ul> <div class="language-python line-numbers-mode"><pre class="language-python"><code><span class="token keyword">def</span> <span class="token function">print_info</span><span class="token punctuation">(</span>name<span class="token punctuation">,</span> gender<span class="token operator">=</span><span class="token boolean">True</span><span class="token punctuation">)</span><span class="token punctuation">:</span>

    gender_text <span class="token operator">=</span> <span class="token string">&quot;男生&quot;</span>
    <span class="token keyword">if</span> <span class="token keyword">not</span> gender<span class="token punctuation">:</span>
        gender_text <span class="token operator">=</span> <span class="token string">&quot;女生&quot;</span>

    <span class="token keyword">print</span><span class="token punctuation">(</span><span class="token string">&quot;%s 是 %s&quot;</span> <span class="token operator">%</span> <span class="token punctuation">(</span>name<span class="token punctuation">,</span> gender_text<span class="token punctuation">)</span><span class="token punctuation">)</span>
</code></pre> <div class="line-numbers-wrapper"><span class="line-number">1</span><br><span class="line-number">2</span><br><span class="line-number">3</span><br><span class="line-number">4</span><br><span class="line-number">5</span><br><span class="line-number">6</span><br><span class="line-number">7</span><br></div></div><p><strong>提示</strong></p> <ol><li>缺省参数，需要使用 <strong>最常见的值</strong> 作为默认值！</li> <li>如果一个参数的值 <strong>不能确定</strong>，则不应该设置默认值，具体的数值在调用函数时，由外界传递！</li></ol> <h4 id="缺省参数的注意事项"><a href="#缺省参数的注意事项" class="header-anchor">#</a> 缺省参数的注意事项</h4> <h5 id="_1-缺省参数的定义位置"><a href="#_1-缺省参数的定义位置" class="header-anchor">#</a> 1) 缺省参数的定义位置</h5> <ul><li><strong>必须保证</strong> <strong>带有默认值的缺省参数</strong> <strong>在参数列表末尾</strong></li> <li>所以，以下定义是错误的！</li></ul> <div class="language-python line-numbers-mode"><pre class="language-python"><code><span class="token keyword">def</span> <span class="token function">print_info</span><span class="token punctuation">(</span>name<span class="token punctuation">,</span> gender<span class="token operator">=</span><span class="token boolean">True</span><span class="token punctuation">,</span> title<span class="token punctuation">)</span><span class="token punctuation">:</span>
</code></pre> <div class="line-numbers-wrapper"><span class="line-number">1</span><br></div></div><h5 id="_2-调用带有多个缺省参数的函数"><a href="#_2-调用带有多个缺省参数的函数" class="header-anchor">#</a> 2) 调用带有多个缺省参数的函数</h5> <ul><li>在 <strong>调用函数时</strong>，如果有 <strong>多个缺省参数</strong>，<strong>需要指定参数名</strong>，这样解释器才能够知道参数的对应关系！</li></ul> <div class="language-python line-numbers-mode"><pre class="language-python"><code><span class="token keyword">def</span> <span class="token function">print_info</span><span class="token punctuation">(</span>name<span class="token punctuation">,</span> title<span class="token operator">=</span><span class="token string">&quot;&quot;</span><span class="token punctuation">,</span> gender<span class="token operator">=</span><span class="token boolean">True</span><span class="token punctuation">)</span><span class="token punctuation">:</span>
    <span class="token triple-quoted-string string">&quot;&quot;&quot;

    :param title: 职位
    :param name: 班上同学的姓名
    :param gender: True 男生 False 女生
    &quot;&quot;&quot;</span>

    gender_text <span class="token operator">=</span> <span class="token string">&quot;男生&quot;</span>

    <span class="token keyword">if</span> <span class="token keyword">not</span> gender<span class="token punctuation">:</span>
        gender_text <span class="token operator">=</span> <span class="token string">&quot;女生&quot;</span>

    <span class="token keyword">print</span><span class="token punctuation">(</span><span class="token string">&quot;%s%s 是 %s&quot;</span> <span class="token operator">%</span> <span class="token punctuation">(</span>title<span class="token punctuation">,</span> name<span class="token punctuation">,</span> gender_text<span class="token punctuation">)</span><span class="token punctuation">)</span>


<span class="token comment"># 提示：在指定缺省参数的默认值时，应该使用最常见的值作为默认值！</span>
print_info<span class="token punctuation">(</span><span class="token string">&quot;小明&quot;</span><span class="token punctuation">)</span>
print_info<span class="token punctuation">(</span><span class="token string">&quot;老王&quot;</span><span class="token punctuation">,</span> title<span class="token operator">=</span><span class="token string">&quot;班长&quot;</span><span class="token punctuation">)</span>
print_info<span class="token punctuation">(</span><span class="token string">&quot;小美&quot;</span><span class="token punctuation">,</span> gender<span class="token operator">=</span><span class="token boolean">False</span><span class="token punctuation">)</span>

</code></pre> <div class="line-numbers-wrapper"><span class="line-number">1</span><br><span class="line-number">2</span><br><span class="line-number">3</span><br><span class="line-number">4</span><br><span class="line-number">5</span><br><span class="line-number">6</span><br><span class="line-number">7</span><br><span class="line-number">8</span><br><span class="line-number">9</span><br><span class="line-number">10</span><br><span class="line-number">11</span><br><span class="line-number">12</span><br><span class="line-number">13</span><br><span class="line-number">14</span><br><span class="line-number">15</span><br><span class="line-number">16</span><br><span class="line-number">17</span><br><span class="line-number">18</span><br><span class="line-number">19</span><br><span class="line-number">20</span><br><span class="line-number">21</span><br></div></div><h3 id="_3-3-多值参数-知道"><a href="#_3-3-多值参数-知道" class="header-anchor">#</a> 3.3 多值参数（知道）</h3> <h4 id="定义支持多值参数的函数"><a href="#定义支持多值参数的函数" class="header-anchor">#</a> 定义支持多值参数的函数</h4> <ul><li><p>有时可能需要 <strong>一个函数</strong> 能够处理的参数 <strong>个数</strong> 是不确定的，这个时候，就可以使用 <strong>多值参数</strong></p></li> <li><p><code>python</code> 中有 <strong>两种</strong> 多值参数：</p> <ul><li>参数名前增加 <strong>一个</strong> <code>*</code> 可以接收 <strong>元组</strong></li> <li>参数名前增加 <strong>两个</strong> <code>*</code> 可以接收 <strong>字典</strong></li></ul></li> <li><p>一般在给多值参数命名时，<strong>习惯</strong>使用以下两个名字</p> <ul><li><code>*args</code> —— 存放 <strong>元组</strong> 参数，前面有一个 <code>*</code></li> <li><code>**kwargs</code> —— 存放 <strong>字典</strong> 参数，前面有两个 <code>*</code></li></ul></li> <li><p><code>args</code> 是 <code>arguments</code> 的缩写，有变量的含义</p></li> <li><p><code>kw</code> 是 <code>keyword</code> 的缩写，<code>kwargs</code> 可以记忆 <strong>键值对参数</strong></p></li></ul> <div class="language-python line-numbers-mode"><pre class="language-python"><code><span class="token keyword">def</span> <span class="token function">demo</span><span class="token punctuation">(</span>num<span class="token punctuation">,</span> <span class="token operator">*</span>args<span class="token punctuation">,</span> <span class="token operator">**</span>kwargs<span class="token punctuation">)</span><span class="token punctuation">:</span>

    <span class="token keyword">print</span><span class="token punctuation">(</span>num<span class="token punctuation">)</span>
    <span class="token keyword">print</span><span class="token punctuation">(</span>args<span class="token punctuation">)</span>
    <span class="token keyword">print</span><span class="token punctuation">(</span>kwargs<span class="token punctuation">)</span>


demo<span class="token punctuation">(</span><span class="token number">1</span><span class="token punctuation">,</span> <span class="token number">2</span><span class="token punctuation">,</span> <span class="token number">3</span><span class="token punctuation">,</span> <span class="token number">4</span><span class="token punctuation">,</span> <span class="token number">5</span><span class="token punctuation">,</span> name<span class="token operator">=</span><span class="token string">&quot;小明&quot;</span><span class="token punctuation">,</span> age<span class="token operator">=</span><span class="token number">18</span><span class="token punctuation">,</span> gender<span class="token operator">=</span><span class="token boolean">True</span><span class="token punctuation">)</span>

</code></pre> <div class="line-numbers-wrapper"><span class="line-number">1</span><br><span class="line-number">2</span><br><span class="line-number">3</span><br><span class="line-number">4</span><br><span class="line-number">5</span><br><span class="line-number">6</span><br><span class="line-number">7</span><br><span class="line-number">8</span><br><span class="line-number">9</span><br></div></div><blockquote><p>提示：<strong>多值参数</strong> 的应用会经常出现在网络上一些大牛开发的框架中，知道多值参数，<strong>有利于我们能够读懂大牛的代码</strong></p></blockquote> <h4 id="多值参数案例-计算任意多个数字的和"><a href="#多值参数案例-计算任意多个数字的和" class="header-anchor">#</a> 多值参数案例 —— 计算任意多个数字的和</h4> <p><strong>需求</strong></p> <ol><li>定义一个函数 <code>sum_numbers</code>，可以接收的 <strong>任意多个整数</strong></li> <li>功能要求：将传递的 <strong>所有数字累加</strong> 并且返回累加结果</li></ol> <div class="language-python line-numbers-mode"><pre class="language-python"><code><span class="token keyword">def</span> <span class="token function">sum_numbers</span><span class="token punctuation">(</span><span class="token operator">*</span>args<span class="token punctuation">)</span><span class="token punctuation">:</span>

    num <span class="token operator">=</span> <span class="token number">0</span>
    <span class="token comment"># 遍历 args 元组顺序求和</span>
    <span class="token keyword">for</span> n <span class="token keyword">in</span> args<span class="token punctuation">:</span>
        num <span class="token operator">+=</span> n

    <span class="token keyword">return</span> num

<span class="token keyword">print</span><span class="token punctuation">(</span>sum_numbers<span class="token punctuation">(</span><span class="token number">1</span><span class="token punctuation">,</span> <span class="token number">2</span><span class="token punctuation">,</span> <span class="token number">3</span><span class="token punctuation">)</span><span class="token punctuation">)</span>
</code></pre> <div class="line-numbers-wrapper"><span class="line-number">1</span><br><span class="line-number">2</span><br><span class="line-number">3</span><br><span class="line-number">4</span><br><span class="line-number">5</span><br><span class="line-number">6</span><br><span class="line-number">7</span><br><span class="line-number">8</span><br><span class="line-number">9</span><br><span class="line-number">10</span><br></div></div><h4 id="元组和字典的拆包-知道"><a href="#元组和字典的拆包-知道" class="header-anchor">#</a> 元组和字典的拆包（知道）</h4> <ul><li>在调用带有多值参数的函数时，如果希望：
<ul><li>将一个 <strong>元组变量</strong>，直接传递给 <code>args</code></li> <li>将一个 <strong>字典变量</strong>，直接传递给 <code>kwargs</code></li></ul></li> <li>就可以使用 <strong>拆包</strong>，简化参数的传递，<strong>拆包</strong> 的方式是：
<ul><li>在 <strong>元组变量前</strong>，增加 <strong>一个</strong> <code>*</code></li> <li>在 <strong>字典变量前</strong>，增加 <strong>两个</strong> <code>*</code></li></ul></li></ul> <div class="language-python line-numbers-mode"><pre class="language-python"><code><span class="token keyword">def</span> <span class="token function">demo</span><span class="token punctuation">(</span><span class="token operator">*</span>args<span class="token punctuation">,</span> <span class="token operator">**</span>kwargs<span class="token punctuation">)</span><span class="token punctuation">:</span>

    <span class="token keyword">print</span><span class="token punctuation">(</span>args<span class="token punctuation">)</span>
    <span class="token keyword">print</span><span class="token punctuation">(</span>kwargs<span class="token punctuation">)</span>


<span class="token comment"># 需要将一个元组变量/字典变量传递给函数对应的参数</span>
gl_nums <span class="token operator">=</span> <span class="token punctuation">(</span><span class="token number">1</span><span class="token punctuation">,</span> <span class="token number">2</span><span class="token punctuation">,</span> <span class="token number">3</span><span class="token punctuation">)</span>
gl_xiaoming <span class="token operator">=</span> <span class="token punctuation">{</span><span class="token string">&quot;name&quot;</span><span class="token punctuation">:</span> <span class="token string">&quot;小明&quot;</span><span class="token punctuation">,</span> <span class="token string">&quot;age&quot;</span><span class="token punctuation">:</span> <span class="token number">18</span><span class="token punctuation">}</span>

<span class="token comment"># 会把 num_tuple 和 xiaoming 作为元组传递个 args</span>
<span class="token comment"># demo(gl_nums, gl_xiaoming)</span>
demo<span class="token punctuation">(</span><span class="token operator">*</span>gl_nums<span class="token punctuation">,</span> <span class="token operator">**</span>gl_xiaoming<span class="token punctuation">)</span>

</code></pre> <div class="line-numbers-wrapper"><span class="line-number">1</span><br><span class="line-number">2</span><br><span class="line-number">3</span><br><span class="line-number">4</span><br><span class="line-number">5</span><br><span class="line-number">6</span><br><span class="line-number">7</span><br><span class="line-number">8</span><br><span class="line-number">9</span><br><span class="line-number">10</span><br><span class="line-number">11</span><br><span class="line-number">12</span><br><span class="line-number">13</span><br><span class="line-number">14</span><br></div></div><h2 id="_04-函数的递归"><a href="#_04-函数的递归" class="header-anchor">#</a> 04. 函数的递归</h2> <blockquote><p>函数调用自身的 <strong>编程技巧</strong> 称为递归</p></blockquote> <h3 id="_4-1-递归函数的特点"><a href="#_4-1-递归函数的特点" class="header-anchor">#</a> 4.1 递归函数的特点</h3> <p><strong>特点</strong></p> <ul><li><strong>一个函数</strong> <strong>内部</strong> <strong>调用自己</strong> <ul><li>函数内部可以调用其他函数，当然在函数内部也可以调用自己</li></ul></li></ul> <p><strong>代码特点</strong></p> <ol><li>函数内部的 <strong>代码</strong> 是相同的，只是针对 <strong>参数</strong> 不同，<strong>处理的结果不同</strong></li> <li>当 <strong>参数满足一个条件</strong> 时，函数不再执行
<ul><li><strong>这个非常重要</strong>，通常被称为递归的出口，否则 <strong>会出现死循环</strong>！</li></ul></li></ol> <p>示例代码</p> <div class="language-python line-numbers-mode"><pre class="language-python"><code><span class="token keyword">def</span> <span class="token function">sum_numbers</span><span class="token punctuation">(</span>num<span class="token punctuation">)</span><span class="token punctuation">:</span>

    <span class="token keyword">print</span><span class="token punctuation">(</span>num<span class="token punctuation">)</span>
    
    <span class="token comment"># 递归的出口很重要，否则会出现死循环</span>
    <span class="token keyword">if</span> num <span class="token operator">==</span> <span class="token number">1</span><span class="token punctuation">:</span>
        <span class="token keyword">return</span>

    sum_numbers<span class="token punctuation">(</span>num <span class="token operator">-</span> <span class="token number">1</span><span class="token punctuation">)</span>
    
sum_numbers<span class="token punctuation">(</span><span class="token number">3</span><span class="token punctuation">)</span>

</code></pre> <div class="line-numbers-wrapper"><span class="line-number">1</span><br><span class="line-number">2</span><br><span class="line-number">3</span><br><span class="line-number">4</span><br><span class="line-number">5</span><br><span class="line-number">6</span><br><span class="line-number">7</span><br><span class="line-number">8</span><br><span class="line-number">9</span><br><span class="line-number">10</span><br><span class="line-number">11</span><br><span class="line-number">12</span><br></div></div><p><img src="media/14993074876434/002_%E9%80%92%E5%BD%92%E8%B0%83%E7%94%A8%E7%A4%BA%E6%84%8F%E5%9B%BEI.png" alt="002_递归调用示意图I"></p> <h3 id="_4-2-递归案例-计算数字累加"><a href="#_4-2-递归案例-计算数字累加" class="header-anchor">#</a> 4.2 递归案例 —— 计算数字累加</h3> <p><strong>需求</strong></p> <ol><li>定义一个函数 <code>sum_numbers</code></li> <li>能够接收一个 <code>num</code> 的整数参数</li> <li>计算 1 + 2 + ... num 的结果</li></ol> <div class="language-python line-numbers-mode"><pre class="language-python"><code><span class="token keyword">def</span> <span class="token function">sum_numbers</span><span class="token punctuation">(</span>num<span class="token punctuation">)</span><span class="token punctuation">:</span>

    <span class="token keyword">if</span> num <span class="token operator">==</span> <span class="token number">1</span><span class="token punctuation">:</span>
        <span class="token keyword">return</span> <span class="token number">1</span>
    
    <span class="token comment"># 假设 sum_numbers 能够完成 num - 1 的累加</span>
    temp <span class="token operator">=</span> sum_numbers<span class="token punctuation">(</span>num <span class="token operator">-</span> <span class="token number">1</span><span class="token punctuation">)</span>

    <span class="token comment"># 函数内部的核心算法就是 两个数字的相加</span>
    <span class="token keyword">return</span> num <span class="token operator">+</span> temp

<span class="token keyword">print</span><span class="token punctuation">(</span>sum_numbers<span class="token punctuation">(</span><span class="token number">2</span><span class="token punctuation">)</span><span class="token punctuation">)</span>

</code></pre> <div class="line-numbers-wrapper"><span class="line-number">1</span><br><span class="line-number">2</span><br><span class="line-number">3</span><br><span class="line-number">4</span><br><span class="line-number">5</span><br><span class="line-number">6</span><br><span class="line-number">7</span><br><span class="line-number">8</span><br><span class="line-number">9</span><br><span class="line-number">10</span><br><span class="line-number">11</span><br><span class="line-number">12</span><br><span class="line-number">13</span><br></div></div><p><img src="media/14993074876434/002_%E9%80%92%E5%BD%92%E8%B0%83%E7%94%A8%E7%A4%BA%E6%84%8F%E5%9B%BE.png" alt="002_递归调用示意图"></p> <blockquote><p>提示：递归是一个 <strong>编程技巧</strong>，初次接触递归会感觉有些吃力！在处理 <strong>不确定的循环条件时</strong>，格外的有用，例如：<strong>遍历整个文件目录的结构</strong></p></blockquote></div></div> <!----> <div class="page-edit"><div class="edit-link"><a href="https://github.com/xugaoyi/vuepress-theme-vdoing/edit/master/docs/00.Python/17.函数进阶.md" target="_blank" rel="noopener noreferrer">编辑</a> <span><svg xmlns="http://www.w3.org/2000/svg" aria-hidden="true" focusable="false" x="0px" y="0px" viewBox="0 0 100 100" width="15" height="15" class="icon outbound"><path fill="currentColor" d="M18.8,85.1h56l0,0c2.2,0,4-1.8,4-4v-32h-8v28h-48v-48h28v-8h-32l0,0c-2.2,0-4,1.8-4,4v56C14.8,83.3,16.6,85.1,18.8,85.1z"></path> <polygon fill="currentColor" points="45.7,48.7 51.3,54.3 77.2,28.5 77.2,37.2 85.2,37.2 85.2,14.9 62.8,14.9 62.8,22.9 71.5,22.9"></polygon></svg> <span class="sr-only">(opens new window)</span></span></div> <!----> <!----></div> <div class="page-nav-wapper"><div class="page-nav-centre-wrap"><a href="/vdoing-demo-repository/pages/e98ba6/" class="page-nav-centre page-nav-centre-prev"><div class="tooltip">16_变量进阶(理解)</div></a> <!----></div> <div class="page-nav"><p class="inner"><span class="prev">
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